Cooling system for lubricating greases



Oct. 12, 1954 A. a. KNIGHT, JR

COOLING SYSTEM FOR LUBRICATING GREASE-S 5 Sheets-Sheet 1 Filed March 23,1950 lb Z Wdbboma Oct. 12, 1954 A. a. KNIGHT, JR 269L278 COOLING SYSTEMFOR LUBRICATING GREASES Filed March 23, 1950 5 Sheets-Sheet 2 5TEAM .1FQE 243, i: KETTLE mania -iOQ lob 104 L05 Gilbert b.(nz5t,dn Unvenbor'Oct. 12, 1954 A. a. KNIGHT, JR 269L 3 COOLING SYSTEM FOR LUBRICATINGGREASES Filed March 25, 1950 i 5 Sheets$heet 3- i l azz l l 1: 1 1 "250i 124 "7-1 1.24 12w mm, 3 I I 1 I l l I I l I I 1' i I I i I: 241-" l 11 n ,1 .1 g 110 g g m 4 I @244 245-1 4h Y a l I 4 b ,Az %Wcmborne.g

Oct. 12, 1954 A. B. KNIGHT, JR

COOLING SYSTEM FOR LUBRICATING GREASES Filed March 23, 1950 5Sheets-Sheet 4 204 z o 'ZO'Z 206 H 205 g 2M- ZOO i 212 FIrS .bg zg A7%,, C Lbborrzeg Oct. 12, 1954 A. B. KNIGHT, JR 2691,278

COOLING SYSTEM FOR LUBRICATING GREASES Filed March 25, 1950 5Sheets-She'et 5 FIG-Co i 145 {40 z l H; l 149-14'? 150 M25 125 S \fz412% FIG Patented Oct. 12, 1954 COOLING SYSTEM FOR LUBRICATING GREASES-Albert B. Knight, Jr., Mount Lebanon, Pittsburgh, Pa., assignor toStandard Oil Development Company, a corporation of Delaware ApplicationMarch 23, 1950, Serial No. l51,450

The present invention relates to a cooling system for lubricatinggreases, and the like. The invention comprises a new type of apparatussuitable for the controlled cooling of lubricating greases and relatedcompositions where it is desired to obtain a definite and controlledcrystalline structure. The invention also involves process aspects, thecontrol of the flow of a cooling fluid, such as air, over containers ofthe material to be cooled being an important aspect.

In the prior art, various attempts have been made to adopt more modernmethods of preparing lubricating greases than the older conventional pancooling processes which are still widely used. In recent years, a numberof inventions have been patented relating to so-called continuousmethods for lubricating grease manufacture. For some types of greases,these continuous methods have proved to be quite satisfactory where thenature of the product permits the type of cooling that can beaccomplished in continuous processes. There are, however, certaingreases which do not as yet lend themselves well to production bycontinuous methods. In some cases, the greases must be cooked forsubstantial periods of time in order to complete the desired chemicalreactions or to fully evaporate water and other reaction byproductswhich should be removed. In some of them, continuous cooling is notpracticable because crystallization must not be allowed to proceed toorapidly because it results in a grease structure which is not suitablefor the purposes intended. For these and other reasons, some of the moreimportant types of lubricating greases, such as those of sodium base,are not generally adaptable to the continuous method of manufacture oreven to the continuous cooling processes which have recently beenadopted for some other types of lubricating greases.

In view of the difiiculties in applying continuous methods to some typesof greases, it is still the practice commercially to prepare importantclasses of greases by the old conventional pan cooling processes. Insuch processes, as is well understood in the art, the grease ingredientsare mixed and cooked in large kettles of appropriate design. Aftercooking has been completed, the hot grease is drawn, while still in amolten liquid or substantially liquid state, into relatively shallowpans which are allowed 'to set without being disturbed for a substantialperiod of time. The cooling of the grease in these pans proceeds at amore or less predeter- 6 Claims. (Cl. 62-114) mined rate that isappropriate for the particular crystalline or colloidal structuredesired in the final composition.

Ordinarily, the conventional cooling pans are relatively shallow indepth although they are of substantial surface area. For example,typical installations may involve the use of several dozen or morecooling pans for cooling the quantity of grease which is cooked in akettle in a single batch. These pans frequently are filled, for example,to a depth of 2 to 5 inches, a depth of about 4 inches being perhaps afair general average, in some installations. When large batches ofgrease which may run, for example, from about 5,000 to 15,000 pounds ormore, are to be cooled after cooking is completed, a very large numberof pans must be filled and spread around on a floor or other supportwhere they are left for a substantial period of time for cooling. Thetime required for cooling these pans of grease depends, of course, onambient temperatures, on the depth of the layers, as well as upon thetemperature of the grease when drawn from the kettle and the temperatureto which it must be cooled before packaging or other processing. Invarioues cases, the cooling time may vary from as little as l or 2 hoursor less to as much as 24 hours or more.

In general, the purpose of cooling lubricating greases in relativelyshallow pans is to obtain the smooth crystalline or colloidal greasestructure which good lubrication demands. When large batches are cooledin the manner described above, there is so much heat involved that whena large number of pans are assembled, for example, spread out on thefloor of a grease plant in the neighborhood of the cooking kettle, thereis not obtained the desired uniformity in structure. Pans of grease nearthe edge of a large area cool more rapidly than those in the center ofsuch an area. Moreover, when pans are placed on the floor, as theycommonly are, there is no circulation of air under the pans and thebottom portion of the grease cools at a different rate than the topsurface. Hence, even in individual pans the cooling is not as uniform aswould be desirable.

It is also desirable, although difiicult to accomplish, to cool a greasecomposition rapidly at first, so as to save in total cooling time, but

it is also desirable that the cooling be carried tain transition stagesWhere crystal, structure changes rapidly. In some cases, it is desirablethat this stage be prolonged or otherwise controlled. This cannotordinarily be accomplished in conventional cooling pans when they aremerely placed on a floor and allowed to set in the ambient atmosphere.Neither is it feasible, in the usual grease making plant, to introducecooled or heated air at a controlled rate so as to maintain accuratecontrol over cooling conditions.

Hence, a. major object of the present invention is to accomplish theuniform and controlled cooling of greases with a minimum of timeconsumption. It is also an object of the invention to provide for theefficient and economical handling and storage of a large number ofgrease cooling pans of conventional type where the kind of grease beingmanufactured requires cooling in such equipment.

It is a further object of the present invention to provide a more orless universal system which can be varied and adapted to various typesof manufacturing operations and to the preparation of various kinds oflubricating greases without major changes in equipment or in methods ofhandling.

These and other objects will become more fully apparent as thisspecification proceeds. Accordingly, reference will next be made to thedrawings forming apart of this specification in which Figure 1 is adiagrammatic view of the apparatus illustrating also the various stepswhich are involved in the present invention;

Figure 2 is a vertical elevational view with certain parts omitted of anapparatus made according to the invention;

Figure 3 is a longitudinal sectional view taken substantially on theline 33 of Figure 2, looking in the direction of the arrows;

Figure 4 is a sectional view of an apparatus substantially like that ofFigure 2, showing certain modified features;

Figure 5 is a top plan view, with certain parts omitted, of part of thedrive mechanism for the conveyors of Figures 2, 3 and 4, this view beingtaken substantially on the line 55 of Figure 3;

Figure 6 is a detailed view in elevation, with certain parts shown insection and other parts omitted, of a pan carrying tray which forms apart of the present invention;

Figure 7 is a front View in elevation of the tray device of Figure 6,portions of the chain conveyors which carry such tray being shown partlyin section.

Referring first to Figure 1, there is shown schematically the outline ofa grease making plant embodying the present invention. A cooking kettleI0 is mounted at a suitable height preferably somewhat above the mainfloor level so that a cooked batch of grease, or the like, may bewithdrawn from the bottom thereof by gravity. As shown in Figure 1, thiskettle is preferably supported by a second or mezzanine floor orplatform, the arrangement being such that raw materials may be fedconveniently into the kettle from a point above the floor lastmentioned. Such mezzanine or upper floor is indicated at l2.

The cooking kettle is provided with a suitable draw-off conduit [4equipped with valve mechanism of appropriate type. This conduit i4 ispreferably wrapped or jacketed with a suitable insulating material toprevent the congealing or hardening of lubricating grease therein whichmight interfere with subsequent operations. In some cases and in thepreferred construction, this draw-off conduit may be steam jacketed sothat it can be heated to melt any residual products that may remaintherein from a previous operation.

Assuming that raw materials have been introduced into the cooking kettle1G and have been suitably stirred and cooked for the desired period, abatch of the cooked lubricating grease is drawn out through the line 14into a series of trays or pans 20. These pans may be supported uponsuitable racks or open tray members 22, only two of which are shown inFigure l. The tray or rack members 22 are each attached, preferably bypivot means, to a pair of conveyor chains or belt 24, 26. Chains arepreferably used, but for some installations belts of suitable weight andmaterial may be employed.

In Figures 1 and '7 each tray is shown carrying two pans 20, but onelarge pan may replace the two. Appropriate retaining means are providedalso to keep the pans in place on the trays as the latter pass throughtheir circuit with the conveyors 24, 26. It will be understood thatcooked lubricating greases may be drawn from the kettle at temperaturesas high as 400 F. or more. For safety of the operators, the constructionis such that any sliding or sloshing is prevented.

The number of trays or racks 22 which can be carried depends upon thelength of the conveyors and also upon the spacing between adjacent racksor trays 22. Preferably, the tower structure is of considerable height,equivalent to several stories of a conventional building, so that a,rather large number of trays and cooling pans may be carriedcontinuously. The size of these trays also can be varied to hold one,two, or more pans each.

The parallel conveyors 24 and 25 are carried and driven by suitabledrums or sprockets not shown in Figure l but shown in the other figuresof drawings to be described hereafter. Both conveyors and the entireseries of trays and pans mounted thereon are substantially enclosed by ahousing structure 30 which preferably extends around all four verticalsides of the conveyor system. Suitable openings are provided, of course,for introducing the filling nozzle M, which is appropriately joined orotherwise made flexible and also for inserting or withdrawing the emptyor filled pans at other convenient points of the conveyor travel. Safetymeans, forming no part of the invention per se, but includingelectrically controlled mechanism for starting and stopping the conveyordrive, are provided so that movement of the conveyor can be stopped orstarted from any opening or control station. These means also preventstarting of the conveyor from one station when a door is open at anotherstation.

It is commonly desirable, for example, to remove the pans of greaseafter they have passed substantially through one complete circuit of theconveyor system and to blend the cooled grease in a blending kettle withsuitable modifiers such as extreme pressure additives, anti-oxidants,other types of greases, and the like. In Figure 1 there is shown aconveyor 35 on the opposite side of, the tower from the cooking kettlewhere the pans may be withdrawn and taken to a blending kettle 46. Forconvenience in other operations, the blending kettle, like the cookingkettle, is preferably mounted at a level substantially above the mainfloor. A roller conveyor, indicated fragmentarily at 4!, Figure 4, maybe provided to carry away the pans and empty them into the blendingkettle 40. The conveyor 4! may comprise an emptying attachment ormovable section for tilting and emptying the trays automatically orsemiautomatically. Another conveyor MA, Figure 4, may also be provided athe lowel level.

As shown in Figure 1, the blending kettle 40 may be mounted in themezzanine or second floor or platform l2 by which it is supported in anyappropriate manner. See also Figures 2 and 4. This kettle has an opening42 at the top into which the pans of cooled or partially cooled greasemay be emptied. The kettle may be provided with suitable mixing meansand with suitable heating equipment. Ordinarily, one of thekettles,preferably the cooking kettle H3, is fireheated so that temperaturessubstantially higher than can be obtainable with steam jackets atavailable plant pressures may be obtained. It is desirable to have theother kettle, preferably the blending kettle 4U, suitably jacketed sothat it can be heated with steam at least to moderate cookingtemperatures without direct fire-heating. The arrangement is such, also,that cooling water or other fluid can be introduced into the jacket.From the blending kettle 40 a withdrawal line 44 is preferably provided.

The grease composition from the blending kettle ordinarily requires nofurther processing, unless homogenizing is desired, and may be feddirectly into containers 5!! such as appropriate drums, cans, or thelike. These containers may be passed along on a suitable conveyor 52which is standard procedure in the prior art and need not be furtherdescribed herein.

Alternatively, where it is not necessary to blend the grease aftercooling, as in the production of block greases which are merely cut intoslabs or blocks of appropriate size after cooling is substantiallycompleted, the grease may be carried down to the main floor and. thepans removed through a suitable conveyor or other handling means 60.

Obviously, the operation of the whole system could be reversed, greasesbeing preparedin the steam jacketed kettle 40, withdrawn into pans 20 ontrays 22 for cooling.

As mentioned above, the entire assembly is preferably substantiallysurrounded by a housing 30 which is provided for the purpose ofconfining the cooling air or other cooling gases to a definite channelaround the pans of hot grease. This housing or enclosure 38 is shownbroken away in Figure 1 in order that the other elements might bepictured more clearly. In actual practice, however, it extendssubstantially from the top to the very bottom of the entire mainconveyor system. Suitable air inlets may be provided at or near thebottom of the main vertical conveyor if incidental'openings areinadequate and appropriate air impelling means also are provided. Thelatter are usually needed not only to circulate cooling air around thegrease pans but also to draw off vapors which are released as the pansare filled with hot grease. The natural draft of the hot vapors andheated air around the grease pans affords some circulation per se butsupplementary draft means usually are needed.

For impelling the flow of cooling air and drawing off the vapors, it isgenerally preferred to use an exhaust fan of appropriate capacity in theventilator mounted on top of a housing structure 12 which surrounds theoperating mechanism for the upper end of the main or vertical conveyor.Obviously, when the exhaust fan is operated, a stream of air is drawnupwardly along the path of the conveyor and around the trays and greasepans, resulting in the cooling of the grease. The removal of the fumesin itself is no small improvement in a practical sense since the olderpan cooling processes passed much of the vapors into the plant from thesteaming freshly drawn pans.

Inasmuch as the incoming air as drawn by the fan mechanism is at itscoolest when it contacts the lowermost grease pans on the rising side ofthe elevator, the coolest air contacts the hottest grease pans. As theair rises in its path, being impelled at a higher velocity than themovement of the conveyor, it overtakes other trays and pans but thetemperature-difference between the air and the grease in the pancontacted thereby becomes progressively smaller. Hence, the air isheated as it rises and the grease is cooled as it rises but the coolingrate as the pans of grease approach the top of the tower becomessubstantially reduced. On the other hand, as the pans begin to descenddown the other side of the conveyor system they meet progressively withcooler and cooler air, the temperature differential being progressivelyincreased. By suitable timing, or by suitable Variation in relativeconveyor speed and air velocity, the critical transition stage ofcooling may be placed where the air is of appropriate temperature togive the correct cooling rate. Moreover, since each pan goes throughexactly the same cycle, all pans are cooled exactly alike. This improvesuniformity over the prior art conventional pan cooling arrangements. Thetemperature and/or humidity of the air which is drawn into the tower maybe controlled if desired.

A further feature of the present invention resides in the particularconstruction of the pan supporting trays by means of which the coolingair has ready access to the bottoms of the grease pans. Hence, thegrease in a given pan can be cooled more rapidly and more uniformly inthis system than in prior art systems where the bottom of the pan wasusually relatively insulated in effect by being placed directly upon aflat solid surface of low heat conductance such as a floor.

The foregoing description covers the general apparatus and its method ofoperation. Referring now to Figure 2, there is shown in somewhat greaterdetail a tower structure mu consisting of appropriate structural membersnot shown in detail but 0f adequate strength and appropriate design tosupport the conveyor system, the power operating equipment above theconveyor system and the exhaust ventilator mechanism above the powerhouse. The power house 12 is of conventional design as is also theventilator system 10.

The tower I00 is supported on an appropriate foundation Hi2 which may beplaced at a level somewhat below that of the main floor I04. A secondfioor I2, as in Figure 1, is suitably sup-. ported by appropriate wallsor other structural member I06 with supplementary footings or foundationelements I08 where these are needed. As previously described, afire-heated kettle I 0 and a steam kettle 40 may be mounted in thesecond or mezzanine floor I2 so that their contents may conveniently bewithdrawn at or above the first or main floor level.

The tower I00 may project beyond the third floor or the roof, as thecase may be, of the factory building or other plant structure dependingupon the height and type of the building in which 7. it is installed. InFigure 2 there is indicated a roof structure I I which is suitablysupported on wall or column elements II 2 which in turn are suitablysupported on the upper or mezzanine floor or on other and generallyequivalent appropriate sup-porting structure.

The tower proper is completely surrounded, except for appropriateopenings hereafter described, by a relatively airtight wall structureI30. This corresponds to the enclosure 30 of Figure 1.

Inside the tower there is provided an upper horizontal shaft I'I4 whichcarries a series of sprockets HE. A horizontal shaft or a group of stubshafts, whichever may be preferred, is mounted at the bottom of theconveyor and indicated generally at H8. On this there are providedsuitable idler sprockets I I9.

Referring now to Figure 3, it will be seen that a pair of conveyorchains I24 and I26 are arranged in parallel relation to pass around theupper sprockets H6 and the lower sprockets II 9. It has been foundadvantageous under some circumstances to mount duplicate units in asingle tower and therefore a second pair of conveyors I24A and IZSA areshown in Figure 3. The number of units in one tower can be varied, ofcourse, to suit specific plant requirements. These additional conveyors,where used, pass around upper sprockets IIBA and around lower sprocketsII9A in the same manner as the conveyors first described. Since theirmanner of operation, however, is exactly the same, the description willbe confined, in general, to the single pair of conveyors I24 and I25.

Between the conveyors I24 and I26 there are pivotally mounted, each in asuspended position, a series of tray members which are shown in Fig ures6 and 7. Thus, in Figure 7 the chain conveyors I24 and I26 are shown inone modification in some detail. At spaced intervals a few links apart,for example, about every 6 or 8 links in one typical installation, thenumber and distance depending, of course, upon the chain structure andother requirements, the conventional link pin I25 is replaced with ashaft I M which extends the full distance between the parallel conveyorchains I24, I25. This shaft I4I supports an anti-friction bearing I42 ateach end, these being shown in detail in the upper left hand and righthand parts of Figure 7.

Each of the tray members 22 comprises an end bracket I40 of generallytriangular shape which has at its upper apex a boss member I43 whichsurrounds the bearing I42. Each end member also comprises a flange I44which stiffens the end member and also rests upon and reenforces theboss I43. The end member comprises a web portion I45 and a reenforcingrib I 46' extending between the web member I45 and the boss I 43. At itslower edge, the web member I45 is secured to an angle bar I41 and eachof the angle bars I4! is provided with a series of bearing apertures I48to receive the reduced end or spindle portions 39 of series of rollersI50.

The two end members are connected not only by the shaft Mi but also by aconnecting member II which extends from one web I45 to the other.

An angle bar I52 is also provided across each lower edge of theassembly, serving further to connect the end members and unite the wholetray assembly. The members I41 and I52 are attached to the webbed andflanged end pieces I49, etc. by appropriate fastening means such asbolts or rivets, or the parts may be welded together. Preferably,however, the assembly is made so that the rollers I59 can be removed orreplaced conveniently should that be necessary.

Each of the sloping flange elements I44 of end members I46 is alsoprovided with an upstanding ear portion I55 which supports a transversetube or shaft member I 56 for limited rotary movement. On each end thisshaft member has a plate I51 afiixed and the plate is so shaped that ithas two stop surfaces I58 and I59 adapted to abut against the foot ofthe ear member shown at I60. Intermediate their ends at a pointapproximately at the middle of each of the pan positions, each of theshafts I55 carries two latch members IBI. Where a single pan is carried,of course only one member IBI need be provided, although two or more maybe used. Each latch member has a stop element I62 directed substantiallyvertically downward and a sloping lifting plate IE3 is afiixed to theend of the latch bar ISI and the stop member I52 by appropriate meanssuch as riveting or welding.

By reason of the construction just described, a grease pan can be slidonto the tray without interference by the latch member which merelylifts up under the force of the pan, but when the pan is pushed fullyonto the tray the latch member I82 will prevent its lateral displacementoff the tray until the latch is lifted. As a pan is slid toward thetray, from the right of Figure 6, for example, its edge will strike thesloping under surface of the lifter I63 which will rise freely and thepan can be pushed on to the tray, riding freely on the rollers I58. Whenpushed fully on to the tray, the pan will contact the stop member I62 onthe opposite side of the tray and the raised latch will then drop to theposition shown in Figure 6 to prevent return movement. It will be notedthat pans may be placed on or removed from any tray from either front orback.

The stop surfaces I58, I59 and IE0 limit rotation of the latch arms IGIin either direction so that the latches are always in position foroperation. If desired, the connecting bar or tube I56 may be made hollow(and in two aligned sections) and supported upon a rod or equivalentstructure obvious to those skilled in the art so that either half can berotated without affecting the other. It is sometimes desirable, as indicated above, to make the tray sufiiciently large to accommodate two oreven more grease pans simultaneously. This depends, of course, upon thesize of pans. Where large pans are used, it may be preferable to carryonly one pan p'er tray. In the case where two pans are carried, it maybe desirable to have independent latches so that one pan remains latchedon the tray while the other is being removed. However, the constructionand arrangement of the trays preferably is such that there is noparticular reason for latching one tray while the other is removed. Thetrays are guided in their travel so that they cannot tilt. Guide meansI'Iil, in the form of vertical rails which hold the trays againstlateral movement are provided along the conveyor for preventing thetilting of the trays due to' unbalanced forces such as an eccentricallydisposed pan of grease. See especially Figure 6 which shows these railsfragmentarily'. They are omitted from the smaller scale figures buttheir construction is believed to be obvious. They extend along the pathof travel beside tray members 22 to prevent tilting particularly atloading and unloading stations and preferably they extend along theentire path of travel.

Referring now to Figure 5, there is shown an appropriate drive mechanismfor operating the main vertical conveyor system. The drive consistsappropriately of a motor 200 with an appropriate brake mechanism 202,the motor being supported on a suitable base 204. The brake mechanism isdesigned to lock the conveyor against inadvertent movement due togravity or otherwise when the motor is stopped. It is preferably of anautomatic or self-setting type. The motor 200 drives a gear reducingmechanism 206 through its shaft 208 and a coupling member 2 I 0. Thegear reducing mechanism comprises a heavy pinion 2 I 2 which drives amain gear 2 I lmounted on the shaft II4 previously referred to.

The large gear 2I4 is keyed to the shaft H4 along with the sprockets H6and the whole assembly of sprockets, gear and shaft is appropriatelysupported in suitable bearing elements 220.

Referring now to Figure 4, there is shown a modification wherein otherparts are substantially unchanged but a center partition is provided toconfine the cooling air to the ascending or descending column of theconveyor without giving it access necessarily to both. This isaccomplished by providing the partition member 230 which substantiallyseparates the ascending elements from the descending elements. Figure 4shows further modifications wherein an opening 232 is provided in thehousing near the top thereof. With this arrangement, air may beintroduced near the top of the conveyor or grease may be removed at thatpoint. Such an operation is not usual but might be desirable in somearrangements.

Both the apparatus of Figure 2 and that of Figure 4 are preferablyprovided with openings and closures on both sides at the second fioorlevel and also at the first or main fioor level. These are indicated at2M, 242, 243, and 244 in both figures. In usual operation, all of thesewould be closed except where pans are being filled or being unloaded, orthe like. For safety of operation, as suggested above, suitable controlsare provided to stop the conveyor when more than one of the closures MI,242, 243, 244 or 232 is open. A full control system for stopping andstarting the main conveyor from any station usually and preferably iscombined with the safety means, as previously suggested.

The reason for this safety mechanism is to provide flexibility ofcontrol but also to give protection for any operator or attendant whomay be inspecting, repairing or conducting some other operation at anyopen station. The conveyor cannot be started by an operator at anotherstation until one or the other has completed his work and closed theopening whereby control of the conveyor is turned over to the otheroperator. The specific means, such as electrical wiring systems, may bevaried and they form. no part of the present invention, but the controland safety feature, as a general adjunct, is of practical importance inthe operation and structure of the invention.

What is claimed is:

1. In apparatus of the character described, the combination whichcomprises a tall tower, a pair of parallel endless conveyors mounted insaid tower and extending substantially through the full height thereof,said tower comprising wall structure substantially enclosing saidconveyor throughout its full length and having access doors on oppositesides near the bottom thereof, a series of open tray members pivotallyattached to and suspended between said conveyors for supporting paths ofmaterial to be cooled, cooperating guide means on said tray members andsaid wall structure for maintaining said tray members in substantiallyhorizontal position during ascent and descent in said tower and meansfor impelling a stream of cooling air upwardly from the lower to theupper portion of said tower around and past each of said trays and eachof said pans to cool said material substantially uniformly and at acontrol ed rate, said enclosed tower substantially confining the streamof air to travel along the conveyor path, a pan loading station near thebottom of the tower on one side and a pan unloading station near thetower bottom on the opposite side.

2. In apparatus of the character described, the combination of a tallenclosed tower, a pair of parallel endless conveyors extendingsubstantially from top to bottom of said tower, a series of tray memberspivotally suspended between said conveyors, cooperating guide means onsaid tray members and inside said tower for preventing tilting of saidtray members during their travel past loading stations, a loadingstation on each of two opposed sides of said tower near the bottomthereof, releasable latch means on each tray member for holding shallowpans in position on said tray members, and air impelling means forpassing and confining a stream of air along the path of said conveyoralong at least the ascending run thereof.

3. Combination according to claim 1 wherein the air impelling meanscomprises a ventilator fan at the top of the tower for drawing airupwardly through said tower.

4. Combination according to claim 2 wherein each tray member has frontand back latch members to permit loading of pans from either side.

5. The process which comprises pouring molten lubricating grease, at atemperature in excess of 300 E, into one of a series of shallow pans,ad-

vancing said pan a short distance, filling the next pan, repeating thisoperation while a long series of pans are filled, continuously passing astream of cooling gas through a conduit substantially enclosing saidseries of pans, so that said gas stream first contacts the pan pouredmost recently and containing the hottest grease, said gas streamthereafter contacting cooler and cooler pans in its passage while itsown temperature increases so that the gas at its warmest point is passedaround and over the pan farthest advanced in the series, and thereafterreversing the direction of advance of said pans so that each panencounters successively a cooler and cooler portion of said gas stream,whereby the cooling rate first becomes progressively slower and laterbecomes progressively faster so that crystallization of the grease isuniformly controlled.

6. In apparatus of the character described, the combination whichcomprises a tall tower, a pair of parallel endless conveyors mounted insaid tower and extending substantially through the full height thereof,said tower comprising wall structure substantially enclosing saidconveyor throughout its full length and having access doors on oppositesides near the bottom thereof, a series of open tray members pivotallyattached to and suspended between said conveyors for supporting pans ofmaterial to be cooled, cooperating guide means on said tray members andsaid wall structure for maintaining said tray members in substantiallyhorizontal position during ascent and descent in said tower, a series ofspaced rollers on each of said tray members, said rollers forming thepan supporting bottom of said tray members to facilitate loading andunloading said pans and to afiord access of cooling air to the bottom ofsaid pans, and means for impelling a stream of cooling air around andpast each of said trays and each of said pans to cool said materialsubstantially uniformly and at a controlled rate, said enclosed towersubstantially confining the stream of air to travel along the conveyorpath.

References Cited in the file of this patent UNITED STATES PATENTS NumberNumber Number Name Date Kind Dec. 3, 1912 Spring June 10, 1913 Gill Aug.3, 1920 Allsop et al. Apr. 12, 1921 Harris Apr. 24, 1928 Baker May 12,1931 Cross Oct. 23, 1945 Patterson Feb. 3, 1948 Houlton Sept. 27, 1949FOREIGN PATENTS Country Date Great Britain July 3 1902

